Fix lldb build on older OSX versions after svn commit r244716

[dawn]

Summary

Older OSX versions don't define NSOperatingSystemVersion, so building lldb gets:

../tools/lldb/tools/debugserver/source/MacOSX/MachProcess.mm:2032:5: error: unknown type name 'NSOperatingSystemVersion'
    NSOperatingSystemVersion vers = [[NSProcessInfo processInfo] operatingSystemVersion];
    ^

This patch fixes the build by having GetOSVersionNumbers return false if ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED < 101000, causing lldb to behave the same as it did before this patch.

[jasonmolenda]

Looks good, thanks, I wasn't sure about whether this API would be available on older releases.

lldb/trunk/tools/debugserver/source/MacOSX/MachProcess.mm

MachProcess::GetGenealogyImageInfo (size_t idx)
     return m_activities.GetProcessExecutableInfosAtIndex (idx);
 }
 
 bool
 MachProcess::GetOSVersionNumbers (uint64_t *major, uint64_t *minor, uint64_t *patch)
 {
     bool success = false;
 
+#if (__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ >= 101000)
     NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
 
     NSOperatingSystemVersion vers = [[NSProcessInfo processInfo] operatingSystemVersion];
     if (major)
         *major = vers.majorVersion;
     if (minor)
         *minor = vers.minorVersion;
     if (patch)
         *patch = vers.patchVersion;
 
     success = true;
 
     [pool drain];
+#endif
 
     return success;
 }
 
 // Do the process specific setup for attach.  If this returns NULL, then there's no
 // platform specific stuff to be done to wait for the attach.  If you get non-null,
 // pass that token to the CheckForProcess method, and then to CleanupAfterAttach.